In recent years, a major development within the petroleum industry has been the discovery of the special catalytic capabilities of a family of zeolite catalyst based upon medium pore size shape selective metallosilicates. Discoveries have been made leading to a series of analogous processes drawn from the catalytic capability of zeolites. Depending upon various conditions of space velocity, temperature and pressure lower oxygenates, such as methanol, can be converted in the presence of zeolite type catalyst to olefins; olefins can catalytically oligomerize to provide gasoline or distillate or can be converted further to produce aromatics. Medium pore size zeolites have also been found to be particularly useful in some fluid catalytic cracking (FCC) operations and dewaxing lube feedstock or fuel oil boiling range materials to produce low pour point lubes or distillate. These, and other, analogous processes have come to be known in the art as the Methanol to Gasoline process (MTG), Mobil Olefins to Gasoline and Distillate (MOG and MOGD), the M2 Forming process for aromatics production, Mobil Distillate Dewaxing process (MDDW), and Mobil Lube Dewaxing process (MLDW).
The conversion of oxygenates is described by C. D. Chang, Catal. Rev.-Sci. Eng., 25, 1(1983) and in U.S. Pat. No. 3,931,349 to Kuo and U.S. Pat. No. 4,404,414 to Penick et al. Conversion of olefins to gasoline and/or distillate product is disclosed in U.S. Pat. Nos. 3,960,978 and 4,021,502 (Givens,Plank and Rosinski). In U.S. Pat. Nos. 4,150,062 and 4,227,992 Garwood et al discloses the operating conditions for the Mobil Olefin to Gasoline/Distillate (MOGD) process for selective conversion of C.sub.3 + olefins. A fluidized bed process for converting ethene-containing light olefinic streams in the Mobil Olefin to Gasoline (MOG) process is described by Avidan et al in U.S. patent application 006,407, filed 23 Jan 1987. The phenomena of shape-selective polymerization are discussed by Garwood in ACS Symposium Series No. 218, Intrazeolite Chemistry, "Conversion of C.sub.2 -C.sub.10 to Higher Olefins over Synthetic Zeolite ZSM-5", 1983 American Chemical Society. U.S. Pat. No. 3,827,968 (Givens et al) discloses a two stage operation wherein a mixed feed containing paraffins and olefins is upgraded in the absence of added hydrogen to a highly aromatic gasoline product. Catalyst dewaxing of lube stock (MLDW) using zeolite catalyst such as ZSM-5 is described in U.S. Pat. Nos. 4,181,598 to Gillespie et al., 4,259,170 to Graham et al. and 4,283,271 to Garwood et al.. Dewaxing of distillate fuel oils (MDDW) is described in U.S. Pat. No. 4,419,220 to LaPiere, et al. and 3,891,540 to Demmel et al. The Demmel et al patent also discloses the use of zeolite catalyst in fluid catalytic cracking (FCC). The foregoing patents are all of common assignee and all of the above references are incorporated herein in their entirety.
In the foregoing referenced processes zeolite catalyst can be regenerated in the conventional manner by contacting the catalyst with oxygen containing gas to effect the controlled burning of coke or other carbonaceous materials from the deactivated catalyst. However, catalyst regeneration by controlled burning of coke produces water which, at high temperatures, adversely effects the structure and activity of the zeolite catalyst. The need exits for better methods to regenerate medium pore zeolite catalyst.
In the prior art, several approaches have been reported regarding improved processes to regenerate zeolite catalysts.
Bowles, in U. S. Pat. No. 3,412,013, teaches contacting a zeolite catalyst with a hydrogen containing gas at temperatures of about 900.degree. F. (482.degree. C. to 1400.degree. F. (760.degree. C.). Haag et al., in U.S. Pat. Nos. 4,508,836 and 4,358,395, teaches the regeneration of deactivated ZSM-5 type catalyst by contacting spent catalyst with hydrogen gas at a temperature of about 800.degree. F. (427.degree. C. to 1200.degree. F. (649.degree. C.). The Bowles patent teaches regeneration with hydrogen in a fluidized dense bed. The Haag et al. patent teaches hydrogen regeneration of a selectively precoked catalyst.
In processes such as MLDW, spent zeolite catalyst is regenerated by treatment with hydrogen to provide a rejuvenated catalyst wherein a major portion of the coke and carbonaceous deposits have been removed. Nevertheless, a more complete removal of these deactivating deposits would more effectively restore catalyst activity and extend catalyst life.
It is an object of the present invention to provide an improved process for the reactivation of spent zeolite catalyst particles.
Another object of the invention is to provide a process for the reactivation of spent medium pore zeolite particles carried out using hydrogen as the rejuvenating agent.
A further object of the present invention is to provide an improved process to extend catalyst life by utilizing hydrogen reactivation or rejuvenation of spent catalyst in conversion processes such as lube dewaxing or olefins oligomerization that use medium pore zeolite catalyst particles.